1. Field of the Invention
This invention relates to an improvement in an aluminum nitride sintered body, and more specifically, to an improvement in the use of a ceramic sintered body composed mainly of aluminum nitride in high-speed machining tools and other applications.
2. Description of the Prior Art
A sintered body of aluminum nitride (hereinafter "AlN") has high thermal conductivity and thermal shock resistance and superior corrision resistance to molten metals, and therefore has attracted attention as thermally stable materials for various uses. Especially in cutting tool applications, AlN generally has a hardness of 70 or less (Rockwell 45 N), and an improved AlN sintered body disclosed in Japanese patent application (OPI) No. 151704/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) has a hardness of 85 at the highest. On the other hand, an alumina-type sintered body has a hardness of 88 to 92. For this reason, ceramic tools made of AlN sintered body have unsatisfactory abrasion resistance. Furthermore, since AlN becomes unstable when heated in the presence of moisture, the production of cutting tools from AlN has not yet been successful.
An AlN sintered body has good electrical insulation characteristics, and by improving the high-temperature corrosion resistance of an AlN sintered body to moisture, it can be employed as cutting tools in various fields. In particular, such AlN sintered bodies can be utilized effectively in machine elements having heat resistance at high temperatures, component parts of gas turbines, and various electrically insulating base materials for high-temperature applications.